Blind rivets and lock bolts, also known as pin and collar fasteners, are common industrial fasteners used in the aerospace and other industries. U.S. Pat. No. 4,347,728, entitled “Apparatus and System for Setting Fasteners,” issued on Sep. 7, 1982, to Walter J. Smith, describes a pulling head for these types of fasteners which is widely used at present in conjunction with commercially available pulling tools. The Smith pulling head includes a unitized gripping jaw assembly that grips and pulls the pin portion of a fastener, a collet that surrounds the jaw and presses the jaws about the pin, and a swaging portion or anvil assembly disposed about the collet that pushes and swages a collar onto the pin and against a workpiece to secure the fastener in place. The collet and the swaging portion are independently and reciprocally slidable lengthwise relative to each other. The Smith pulling head can apply tensile and compressive forces as great as several thousand pounds.
Many situations arise where a fastener must be installed in a workpiece where the space is inadequate to accommodate the pulling head. In particular, these situations may arise during maintenance or repair of aircraft or other industrial objects. The original fastener may have been installed prior to assembly of nearby components, allowing use of a standard pulling head. However, complete disassembly for repair or maintenance may be inconvenient, impossible, time-consuming, and/or costly.
One possible solution would be to decrease the wall thickness of the cylindrical anvil sleeve and/or the cylindrical collet to provide a smaller outer diameter for the anvil sleeve. However, this is undesirable, because decreasing the overall wall thickness of the sleeve or the collet would also decrease its strength, making it prone to failure under the forces to which it is subjected during fastener installation.
Thus, there is a need for a pulling head for installing blind rivets, blind bolts, and lock bolts that allows installation of the fasteners in tight areas close to obstructions extending outward from a workpiece without compromising the compressive and tensile strength of the pulling head.